The present invention relates to a cassette for band, tape or ribbon material, such as e.g. photographic film.
More particularly--but not exclusively--the invention relates to a motion picture film cassette having a film supply spool, a film take-up spool coaxial thereto, and a device for preventing rewinding of the exposed film from the take-up spool onto the supply spool.
Motion picture film cassettes for amateur films (i.e. 8 mm and Super-8) having these general features are already known in the art, for example from German Gebrauchsmuster 7, 112, 162, German Pat. No. 2,126,636 and German Published Application No. 2,538,425.
The prior-art cassettes are suitable for their intended purpose. However, further improvements are desirable for a variety of reasons. For example, in one type of prior-art cassette the reverse movement of film is prevented by cooperation of a blocking finger with a blocking tooth. This arrangement is satisfactory if unwinding of the film by almost one complete convolution is acceptable. If this is not acceptable, then a plurality of the blocking teeth must be provided. Moreover, the finger and teeth are provided in an annular hollow formed in the take-up spool. As a result this spool, which is produced by injection molding, becomes quite expensive because it can be produced only with the aid of a complicated (and hence costly) mold.
Similar problems exist in other prior-art cassettes which can be produced only with complicated, costly molds.
Cassettes of this type are mass-produced in very large quantities and it is evident that manufacturing savings of even small or very small magnitude will cumulatively result in very sizable cost reductions, which can be passed along to the consumer.